Problem: Ishaan is $72$ years old and William is $4$ years old. How many years will it take until Ishaan is only $5$ times as old as William?
Answer: We can use the given information to write down an equation about how many years it will take. Let $y$ be the number of years that it will take. In $y$ years, Ishaan will be $72 + y$ years old and William will be $4 + y$ years old. At that time, Ishaan will be 5 times as old as William. Writing this information as an equation, we get: $72 + y = 5 (4 + y)$ Simplifying the right side of this equation, we get: $72 + y = 20 + 5 y$. Solving for $y$, we get: $4 y = 52$. $y = 13$.